How many genes are in each cell?
Somatic cells usually have one copy of chromosomes 1-22 from each parent, plus an X chromosome from the mother, and either an X or Y chromosome from the father, for a total of 46. There are an estimated 20,000-25,000 human protein-coding genes.
Genes, which are made up of DNA, act as instructions to make molecules called proteins. In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases. The Human Genome Project has estimated that humans have between 20,000 and 25,000 genes.
- Genes are made of a chemical called DNA, which is short for 'deoxyribonucleic acid'. The DNA molecule is a double helix: that is, two long, thin strands twisted around each other like a spiral staircase. The sides are sugar and phosphate molecules.
- Genes contain DNA (deoxyribonucleic acid). DNA is the chemical basis of heredity. Think of it this way: DNA is in genes, genes are on chromosomes. When "mapping" all genes on all human chromosomes was first seriously conceived, it was called the Human Genome Project - a combination of gene and chromosome.
- Researchers refer to DNA found in the cell's nucleus as nuclear DNA. An organism's complete set of nuclear DNA is called its genome. Besides the DNA located in the nucleus, humans and other complex organisms also have a small amount of DNA in cell structures known as mitochondria.
The human genome contains approximately 3 billion of these base pairs, which reside in the 23 pairs of chromosomes within the nucleus of all our cells. Each chromosome contains hundreds to thousands of genes, which carry the instructions for making proteins.
- In genetics, the gene density of an organism's genome is the ratio of the number of genes per number of base pairs, usually written in terms of a million base pairs, or megabase (Mb). The human genome has a gene density of 12-15 genes/Mb, while the genome of the C. elegans roundworm is estimated to have 200.
- 241.html). If there is a value of around 50% gene-share between banana and humans, it would be interesting to know how the DNA was actually compared! Presumably by 'genes' people are referring to the predicted protein-coding genes, approx 36,000 in the banana genome which is more than that predicted in humans.
- Somatic cells usually have one copy of chromosomes 1-22 from each parent, plus an X chromosome from the mother, and either an X or Y chromosome from the father, for a total of 46. There are an estimated 20,000-25,000 human protein-coding genes.
Before the completion of the human genome project, many scientists were expecting to find 100,000 or more genes in our genome. This was based on the assumption that because we are one of the most complex creatures on Earth we should have lots of genes. However, it turned out we only have around 24,000 genes.
- A gene is the basic physical and functional unit of heredity. Genes, which are made up of DNA, act as instructions to make molecules called proteins. In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases.
- Genes are found on long strands of DNA called chromosomes. Most humans have 23 pairs of chromosomes. So they have two copies of chromosome 1, two copies of chromosome 2, etc. You get one copy of each of your chromosomes from your mother and one from your father.
- In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure.
Updated: 11th October 2018